I have a really stupid problem here and thought maybe you guys could
help me improve my understanding..
I have a tiny audio program. It consists of two threads. The first
thread uses the xinelib for audio output and reads its input from a
fifo. The second thread creates a sine wave, "converts" it into
WAV/PCM16 format and sends it to the fifo. After it has sent the first
WAV/PCM16 chunk it keeps on looping but only sends the PCM part of the
sine wave without the WAVE header.
Now my problem: the second thread (=sine thread) uses a buffer where it
generates the sine data. Once that buffer is full it writes the whole
buffer to the fifo.
What I experience is that what I hear depends on the size of this
buffer. When I set the buffer size to 44100 samples (which I think
equals 1 second of sound) then I hear a proper sine wave at the right
frequency. When I change it to 22050 still ok. But once I choose for
intance 11025 or 16384 or 8192 or 4096 I get strange stuttering, clicks
or a somewhat modulated sound.
So I thought the problem is my sine generator and compared the output
using different buffer sizes. But it's the same no matter what buffer
size I use.
I can post some code too if that helps and would be grateful for any help.
Thanks
mimo
Sorry if multiple copies of this appear. The spam filter doesn't like my
choice of titles. I've tried a few variations so far.
I'm looking to develop a music editor/sequencer somewhat in the vein of
Cakewalk/Rosegarden, but looking more towards the future of MIDI and audio
capabilities. I've been thinking about this for a long time, and I think I
have enough of a plan now to make a go at it.
This is a rather long post, so I've divided it into four parts: Why Not
Rosegarden?, Project Overview, Design Goals, and End Notes.
Why Not Rosegarden?
Why not just join the Rosegarden devlopment team? While Rosegarden has a lot
of promise, it's design goal is different than what I'm thinking of. To put
it crudely, Rosegarden's goal is to be a better Cakewalk. This isn't meant to
be disrespectful to the Rosegarden developers. I like Cakewalk. (If you
don't, substitute CueBase, or whatever professional tool of that genre.)
Music is a language. While music itself is much more complex and vague (like
natural language) than a programming language such as C, I will use the
analogy of a programming editor. Rosegarden (and all similar tools) is like a
C editor. When it's mature, it will be a very good C editor. In addition, the
modularity and generalized approach that Rosegarden uses will make it
possible to also be a good C++ editor. I'm thinking of something more like a
multi-editor that will work for Perl or lisp. It will have it's own
limitations, so I'm not trying to create the be-all end-all of music editors.
But there are some fundamental things that Rosegarden will never be able to
accomplish. (An most users won't have any reason to want an editor that will
accomplish these things.)
The first involves the way meter and tempo are handled. There are several
pieces of 20th century music that incorporate 2 or more voices playing
simultaneously in 2 or more meters. An example that chokes every editor I
know of (though I'm told lilypond can do it with difficulty, but it has no
sequencing capability and isn't a WYSIWYG) is Bartok's "Music for Strings,
Percussion, and Celeste". I'm not saying that you can't create a Rosegarden
file that will play this piece. What I am saying is that the notation will be
extremely ugly. The issue is that not all of the voices are playing
simultaneously in the same meter. To notate this in all in one meter means
that some of the voices will look extremely complicated with myriads of ties
and accent marks.
Another interesting thing is to have 2 voices playing with different tempo.
No examples come to mind, but I can think of some cool effects that could be
achieve by having one voice race ahead of another. Again, Rosegarden could
play such a piece, but the notation would be ugly.
A third thing revolves around scales and tunings. Rosegarden has some plans
for different tunings and perhaps support for quarter tones. And I think,
again, that a Rosegarden tuning would be applied to an entire composition,
not a single instrument. But I'm thinking of things more general. Suppose
each track had an element called "tuning". Suppose also that each note is
stored as an integer in a note event (as it is in Rosegarden). The tunings
element contains a mapping between the note number given in the event and
what is actually played. Microtones and temperaments could be stored in the
tunings file as a MIDI note number plus a pitch bend. (Or we could store
frequencies, and some function converts frequencies to MIDI note numbers plus
pitch bends.) More novel things (such as octaves that aren't quite perfect
frequency multiples) could also be accommodated. The tunings file could also
be used to define scales that include added scale degrees. (e.g. for a
Pythagorean tuning, we have to include extra values, so we can notate, say,
an F## instead of a G, as these tones may not be equivalent in a non-equal
temperament.)
Rosegarden is trying to be fairly general about instrument definitions, which
is good. I'm thinking of somewhat different approach that looks to the future
of MIDI, in which we want to achieve more realism of the performance. Each
Track has this abstract thing called an Instrument. Instruments may be atomic
(a string) or composite (a guitar, which is composed of several atomic string
instruments). Let's suppose we use soundfonts. We could create a soundfont
with banks 1-6 for the strings of a guitar. Each single-string Instrument
gets mapped to one of the tone banks, and the guitar Instrument is composed
of these single-string Instruments.
In this way, it would be possible to achieve a playback in which an open D
chord sounds different than a 5th position D chord played a string lower,
just like on a real guitar. Instruments should have "modes" which can be
selected (and changed within the song). A guitar might have pickstyle
(perhaps which eventually get mapped to tonebanks 1-6) and fingerstyle (which
eventually get mapped to tonebanks 7-12). An organ could have modes for
various configurations of the stops. We could get very elaborate here and
have organs with multiple keyboards, etc., but I'm falling into a dreamy
state here. The idea is that the design should allow for this type of
functionality to be added.
So, how can we accomplish such a beast? Let's take a tour of what's in my
brain. No, no! Not over there! Don't open that door. That's the basement
where all the beastly details hide. Whatcha mean it's empty? Of course it's
empty. No, not that door either. That's the closet of confusion and
inconsistency. This way, this way. Here's the beautiful entry...
Project Overview
No pretty pictures, so you'll just have to imagine.
We begin with a main window. The document-view model is appropriate. We'll
have the typical views that you'd expect -- TrackView, ScoreView (StaffView),
MixerView, and some sort of EventView.
TrackView should look similar to that of Rosegarden, but we need to implement
it differently. The window needs to be some sort of split window, in which
each track gets its own pane. At the top, should be a time ruler which can
display in seconds, SMPTE, or beats/measures of a track. It should default to
displaying beats/measures of track 1. Each track pane displays its clips
similar to Rosegarden/Cakewalk. But it should hold a TrackGroup instead of a
single Track (Byt default each Track is in its own group). Additionally, it
should have a hideable ruler that displays time (default to beats/measures)
and tempo markings for that TrackGroup. This means that the TrackGroup data
structure needs to hold info about its meter and tempo. TrackGroups can be
expanded to show each track. They can also be hidden to reduce clutter.
TrackGroups can be nested (e.g. strings, violins, violin1). During playback,
big vertical ruler bar should follow the sequencer, similar to the appearance
in Rosegarden.
ScoreView should display like a score with staff notation. Tracks can be
grouped, and it should be possible to hide groupings. Expanded track
groupings should show each track. When compressed, a single staff with
multiple voices (1 for each track) should be shown. In this way, 4-part
harmony, drums, etc. can be displayed as is most convient to the user.
Tracks should be displayed with appropriate staves (single 5-line staff for
voice, optional tablature for stringed instruments, etc.) Non-MIDI tracks
such as wav audio should be displayed as a simple line or bar. We should
include typical musical symbols, dynamics, guitar tab symbols, lyrics,
section markers, and effects markers (things like echo, flange, etc.) Each
track should have an option to hide various things (e.g. hide the tablature,
lyrics, or effects markers).
Eventually, we should be able to print out sheet music.
The MixerView should be pretty typical, but again, with the ability to create
a nesting of sub-mixers. Each track should get its own effects rack.
Additionally, each sub-mixer (or track group) should get an effects rack.
This way, we can set effects for individual instruments. Then we can layer
another level of effects (say panning or delay) to a group. Finally, we can
add a layer for everybody (say reverb). As much as possible, we shouldn't
care whether we're dealing with wavs or MIDI. If we have a MIDI track, the
popup menu should only display MIDI effects. For aggregate groupings, only
effects that can be used on either MID or wave should be available. (Perhaps
we can take existing MIDI or audio only effects and put wrappers around them
that select which effect is actually used.) Supporting plug-in effects would
be very good. In the end, though, I think effects should be handled in the
same way as instruments. That is, we build complex effects out of simpler
components.
This leads me to instruments. Instruments and effects should be stored in
definition files. Then we can set up our instruments once and use them in
multiple compositions. Ditto for tunings.
Files should be stored as XML (probably compressed, as Rosegarden does).
Design Goals
1) Flexibility is paramount. A rigid desisn isn't going to work here. There
are too many unknowns and open-ended issues.
2) Modularity. Keep the pieces as independent as possible. Try to make
generic base classes that defer as much of the details as possible to derived
classes.
3) Begin with a generic framework. Determine how the system should operate.
Do we run the whole thing like an IDE for a programming language? How
separated should the editor and sequencer be? Do we edit, save to file, and
compile (sequence)? Or should the sequencer be more closely coupled, causing
the data structures in memory to be shared between editor and sequencer? The
first approach would make it difficult (or impossible) to do realtime mixing
of MIDI tracks, but it would provide for very efficient playback. All of the
MIDI tracks would be compiled to a MIDI file, so the on-the-fly processing
would be minimal. Efficient, but limiting. Perhaps it should run more like an
interpreter, processing the file on demand. A "mixdown" option could be
added, that would compile everything down for a final release. Then anyone
with the sequencer could play the file. (Analoguous to Windows Media Player,
in which you can play .avi files, but you can't create or edit them.)
4) Simple things should be simple. The default should be that every track
plays at the same tempo and in the same meter, instruments should map to
General MIDI bank, and equal-temperament tuning with standard key signatures
should be used. Recording, playback, and basic editing should be easy and
intuitive. The most common features and feature groupings should appear in
the menus. An advanced tab should be present to allow for lesser uses
features.
5) Don't lose sight of the big picture. The end goal is to have a product
that allows for audio and MIDI tracks that will play in sync. Other types of
tracks (such as video, or images) could be included as well.
6) Get something that's useful and provides basic functionality up and
running quickly. Add features step by step. A brilliantly conceived program
isn't worth much if it doesn't run.
7) I'm leaning toward C++ as the primary language, though it may be better to
use a scripting language such as Perl (which I know) or Python (which I don't
know) for certain portions. My most common methodology involves writing a
core engine in C++, then developing a simple scripting language (usually in
Perl) to access the features of the core. I'm not sure such an approach is
appropriate here, though.
End Notes for the Curious
I used to be a software designer and programmer. I've been stagnant for
several years now due to an illness that's taken away my presenability in job
interviews. (It's hard to make a good impression in today's world of
corporate fluff where appearance is more important than ability when you look
haggard, shake like an addict in detox, and have periods of brain fog that
never fail to appear in an interview.)
I don't know all that much about the down and dirty of audio programming. I
wrote a little media player tool with DirectX in Windows, a linux tool that
converts files between MIDI and XML (I should probably stick this out there
one SourceForge, as someone else might think it useful. How do I do that?),
and a few other little audio utilities.
I know a good deal about software design and maintenance, and I'm proficient
in c++ (and a few other languages as well). I've been project leader on a few
different pieces of software of substantial (100k-200k lines) size, with
teams of 10 people of less.
My degree is in applied mathematics.
For any university professors out there, I think this would be a great
master's (or phd) thesis. And I just might know a pretty good candidate. ;)
Hi all (especially Fons!)!
I've just successfully compiled and installed aeolus (lastest release). I
can start the program connect it to jack and alsa midi seqeuncer, but there it
stops. I asked a seeing companion of mine to have a look at the ui, but even
after pressing several buttons, there was no sound.
Now my questions:
1. Is this a bug or just me and my friend being to stupid?
2. Are there shortcuts/hotkeys, so I can use the organ myself without help?
3. Are there maybe other ways to use it vai "remote control" (OSC, etc.)?
I'm greatful for any good suggestions and hints!
Kindest regards
Julien
P.S.: I read the installation instruction and directory/configuration hints
very carefully, it shouldn't be that... :-)
--------
Music was my first love and it will be my last (John Miles)
======== FIND MY WEB-PROJECT AT: ========
http://ltsb.sourceforge.net - the Linux TextBased Studio guide
Attached is a pdf containing the job announcement for Director of
Technical Support at Radio Free Asia. We use Linux and Free Software
for most of our network information systems and also for a number of
middleware applications that glue together our various proprietary audio
systems. We also have users beginning to test Audacity as a replacement
for Cool Edit. In the future I see a place for Ardour as a replacement
for our 30+ aging Orban Audicy(tm) DAWs, Audacity as a replacement for
Cool Edit, icecast/ogg-vorbis/ecasound to replace our hardware mp3
encoders for streaming and archiving and perhaps other uses of linux
audio software as well.
Address any replies to jobs(a)rfa.org
Thanks,
--
Eric Dantan Rzewnicki | Systems Engineer I
Technical Operations Division | Radio Free Asia
2025 M Street, NW | Washington, DC 20036 | 202-530-4900
CONFIDENTIAL COMMUNICATION
This e-mail message is intended only for the use of the addressee and
may contain information that is privileged and confidential. Any
unauthorized dissemination, distribution, or copying is strictly
prohibited. If you receive this transmission in error, please contact
network(a)rfa.org.
Announcing blepvco 0.1.0:
http://home.jps.net/~musound/blepvco-0.1.0.tar.gz
blepvco is a LADSPA plugin library containing three anti-aliased,
minBLEP-based, hard-sync-capable oscillator plugins. The
oscillators are intended to be used with modular synthesis systems,
such as Alsa Modular Synth (a couple example AMS patches are
included). The three oscillators are:
Sync-Saw-VCO : Anti-aliased sawtooth oscillator with hard-sync
capability
Sync-Rect-VCO : Anti-aliased variable-width rectangle oscillator, with
sync
Sync-Tri-VCO : Anti-aliased variable-slope triangle oscillator, with
sync
Users of Fons Adriaensen's VCO-plugins will find these plugins
immediately familiar, since they borrow much of their interface code
from Fons' work -- indeed, if/when you do not need the hard-sync or
variable-slope triangle wave features of blepvco, his plugins may be
a better choice, because their CPU use is somewhat lower. Currently,
his VCO-plugins can be found at:
http://users.skynet.be/solaris/linuxaudio/
blepvco is written by Sean Bolton, and copyright (c)2005 under the
GNU General Public License, version 2 or later. Much thanks to Fons,
Daniel Werner, Tim Stilson and Julius Smith, and Eli Brandt.
Congratulations to comix & crew !
This just in:
From: Comix <acominu(a)tiscali.it>
To: ML Hydrogen-devel <hydrogen-devel(a)lists.sourceforge.net>
Cc: hydrogen-users(a)lists.sourceforge.net,
hydrogen-announce(a)lists.sourceforge.net
Date: Tue, 01 Feb 2005 16:24:55 +0100
Subject: [Hydrogen-devel] Hydrogen won in 1st italian Open Source Contest
http://www.opensourcecontest.it/index.php?sezione=premiazione
Thanks all! ^_^
-- comix
// Sorry for crossposting, I have got the only reply at the LAU list :-(
Hi,
Will be glad to get your opinions about choosing an audio
card below $250. The main (and, probably, the only) planned
using is a playing back of stereo files. Probably, a DAC
quality is the main feature here.
With hope,
Andrew
Greetings:
When I use jack_fst with the Crystal synth it works fine, but when I
close the plugin qjackctl closes too. Its settings remain in effect, but
the GUI vanishes. If anyone else has this problem, please let me know if
you've found a fix for it. It's annoying to have to reopen qjackctl each
time I use jack_fst.
jack_fst 1.2, qjackctl 0.2.14
Best,
dp
I meed to communicate with MIDI devices from an embedded Linux world
(Gumstix). Its UARTs are cabable of:
14.7456M/16*29 = 31779
14.7456M/16*30 = 30720
MIDI spec says +-1%. My error is 1.7%, Is this close enough?
I figure this problem can't be new, but I'm finding very little info
about it. Some sites hint that an error of up to 3% is OK with certain
MIDI devices.
Any advice appreciated,
darren
